The field of the present invention relates to archery bows. In particular, a compound archery bow is described herein wherein a power cable take-up mechanism has an effective lever arm that decreases to a distance less than the axle radius during a latter portion of drawing the bow.
For purposes of the present disclosure and appended claims, the terms “compound archery bow” or “compound bow” shall denote an archery bow that uses a levering system, usually comprising one or more cables and pulleys, to bend the limbs as the bow is drawn. Examples of compound bows include dual-cam bows (including those that employ a Binary Cam System®), hybrid-cam bows, or single-cam bows. Many compound archery bows typically include one or more power cables (sometimes referred to as buss cables or anchor cables). Conventionally, each power cable is engaged at its first end to be taken up by a power cam (or other take-up mechanism) of a pulley member rotatably mounted on one bow limb, and is coupled at its second end to the other bow limb (in some cases a fixed connection, and in other cases including a mechanism for taking-up and/or letting-out the second end of the power cable). Tension developed as the bow is drawn and the power cable is taken up causes deformation of the bow limbs and storage of potential energy therein. A portion of that potential energy is transformed into the kinetic energy of the arrow shot by the bow. A few examples of various compound bow types are disclosed in the following patents and application, all of which are incorporated by reference as if fully set forth herein:    U.S. Pat. No. 3,990,425 entitled “Compound bow” issued Nov. 9, 1976 to Ketchum;    U.S. Pat. No. 4,686,955 entitled “Compound archery bows” issued Aug. 18, 1987 to Larson;    U.S. Pat. No. 5,368,006 entitled “Dual-feed single-cam compound bow” issued Nov. 29, 1994 to McPherson;    U.S. Pat. No. 6,871,643 entitled “Eccentric elements for a compound archery bow” issued Mar. 29, 2005 to Cooper et al;    U.S. Pat. No. 6,990,970 entitled “Compound archery bow” issued Jan. 31, 2006 to Darlington;    U.S. Pat. No. 7,305,979 entitled “Dual-cam archery bow with simultaneous power cable take-up and let-out” issued Dec. 11, 2007 to Yehle;    U.S. Pat. No. 7,441,555 entitled “Synchronized compound archery bow” issued Oct. 28, 2008 to Larson;    U.S. non-provisional application Ser. No. 12/511,085 entitled “Pulley-and-cable power cable tensioning mechanism for a compound archery bow” filed Jul. 29, 2009 in the name of Craig T. Yehle; and    U.S. non-provisional application Ser. No. 12/690,783 entitled “Eccentric power cable let-out mechanism for a compound archery bow” filed Jan. 20, 2010 in the name of Craig T. Yehle.